1. Field to the invention
The invention relates to a data processing device, more particularly adapted to a chained computer language, especially of the FORTH type, which device comprises inter alia:
a main memory for containing an execution program with its instruction data formed by a plurality of instructions which are directly executable or indirectly executable, the latter being arranged in at least one sub-program, PA1 a first stack-type memory for containing the address following the address calling a sub-program (return address), PA1 one or several operational units for executing the instructions which can be directly executed, each of which may contain: PA1 a second stack-type memory for containing parameters used by the said program, PA1 an instruction-decoding member for decoding each instruction data coming from the main memory.
2. Related Art
Such a device is described in European Patent no. 0 185 215.
To design an execution program, the programmer or language compiler must know the hardware resources with which the device operates. Thus he must know whether each particular instruction can be directly executed or whether it must be diverted to a sub-program which carries out the function by means of directly executable instructions. For example, if a multiplier member is provided in the device, the multiplication operation is directly executable, but if this member is absent, it is necessary to call a multiplication sub-program which operates by successive addition and shift operations. This choice is laid down by means of a binary element incorporated in the instruction put in by the programmer for indicating whether the instruction is directly or indirectly executable. In other words, it is necessary to compile with an indicator for providing either directly executable instructions or a reference to a library which emulates the absent instruction.
The fact that the user must know the resources forms a first disadvantage.
A second disadvantage connected therewith is that the program, once established, can only function with the device in conjunction with the environment for which the program was designed, and addition of other material resources means that the program must be written or compiled anew.